My invention relates to a shoring device comprising a piston, cylinder and removable swivel side plates combined with either an (i) inner ratcheting ring or (ii) pin and collar ring. More particularly, this invention relates to a shoring device with two removable side plates which attach to a cylinder and/or piston with a détente sphere attachment. Each détente sphere inserts within a corresponding aperture of a piston or cylinder. These removable swivel side plates with détente sphere attachments insure reliable attachment to the cylinder and piston without the expense, extra weight and handling of détente pins or other attaching and connecting devices.
In experimental trials, my pneumatic shoring device withstood pneumatic pressures within the cylinder of at least 300 psi (pounds per square inch) for a minimum of fifteen seconds. My new device is intended for, but not exclusively, public works and construction, rescue and other projects in which shoring is necessary.
As workers shore trenches, they must quickly install shoring to prevent collapse of the trench walls. If shoring is not installed, soil cohesion is lost and it becomes almost impossible to maintain a safe trench. The prior art as best depicted in expired U.S. Pat. No. 3,851,856(Berg) provided a shoring device with an inlet connecting to a pressure source for expanding the device tightly against trench walls. There is also a rotational outer ratcheting ring mounted on one cylinder end, which receives the piston. This rotational outer ratcheting ring extends axially from the cylinder and surrounds a proximal piston end.
Still referring to the Berg device, the rotational member is prevented from rotation in part by a cam-like ridge along the proximal member edge. Subsequent to cylinder pressurization the piston remains extended by securing the cam-like ridge on the rotational member with an abutting cam pin. However the only structure in Berg's device which prevents the piston from random axial movement projectile is a small diameter pin. This small diameter pin penetrates the rotational member and abuts the cylinder, after the abutting cam pin is already in place. The small diameter pin end abuts the cylinder, and can be further tightened against the cylinder by a t-bolt.
Berg does not disclose removable swivel side plates which (i) attach to the piston or cylinder with a spring biased détente sphere; and which (ii) reversibly protrude within corresponding cylinder or piston apertures. In contrast, my new shoring device comprises removable swivel side plates, each with a single, or two opposing détente sphere attachments. In one prototype an inner ratcheting ring preferably attaches to the cylinder with allen screws (threaded with hexagonal head depressions), as well as by a circular metal lip which engages one cylinder end. The inner ratcheting ring reduces the likelihood that the piston becomes a projectile. This safety feature occurs because the piston abuts the inner lip, and so the piston cannot move laterally. This outer ratcheting collar is described in detail in U.S. Pat. No. 6,746,183 B1.
The outer removable ratcheting collar encloses the inner ratcheting ring and interlocks with inner ratcheting ring serrations. Outer ratcheting collar preferably comprises one rectangular protrusion which interlocks with the inner serrated ring. This interlocking prevents counter-clockwise rotation of the outer ratcheting collar, thereby preventing collapse of the piston upon the ground or floor.
With respect to the pin and collar shoring device, described previously in application Ser. No. 10/826,093, a continuous circular indentation prevents the flat threaded pin furthermost point from skidding along the cylinder surface. The cylinder is not weakened by repeated contract, because the outer cam collar provides the direct contact surface. My outer cam collar is more economical to replace, and protects the cylinder from wear and tear from the threaded pin.
In addition, my inner pin and collar shoring device comprises a continuous circular lip which abuts the piston and prevents it from falling from the cylinder or becoming a projectile during operation. My new inner ring engages one cylinder end, thereby reducing the possibility that the piston will fall from the cylinder during operation. This metal lip abuts the piston to prevent piston lateral movement, which is an important safety advantage which over Berg's device.
The modified pin collar shoring device also comprises the same removable swivel side plates with détente sphere attachments which (i) contain small spring biased détente spheres, and (ii) reversibly attach each removable swivel side plate without additional cumbersome détente pins or other attaching devices. With the pin and collar model, the outer cam collar encloses the inner ring and comprises the threaded pin which tightly abuts the circular continuous indentation. The cam edges, together with a straight metal cam pin, prevent counter-clockwise rotation of the outer cam collar. This improved pin and collar shoring device is engineered to assist underground workers in compliance with the OSHA regulation governing excavations, i.e., 29 C.F.R. 1926.650. In sum, this new shoring device, in either prototypes and with either a single or an opposing pair of détente sphere attachments, solves a problem in the art which Berg does not resolve.
Shoring is the placement of cross bracing and other components within a trench to support trench walls. There are two important theories of shoring: first is the theory of “zero-movement”, in which shoring is designed to prevent wall movement. Shoring is not sufficiently strong to retain a moving wall of soil: it merely prevents a soil wall from initially moving. The second theory of shoring is designated the “Arch Effect.” Shoring is effective because it creates forces as it pushes again trench walls. The network of cross braces and uprights or wale-plates creates an arch effect which retains soil. The shoring and cross bracing actually retains soil, and not the plywood or sheeting.
An operator applies plywood or sheeting to prevent surface soil from falling and injuring a worker. To achieve “zero movement” and the “arch effect,” all gaps and voids must be filled where the cross brace bears on the trench wall. Other than the mandatory inspection for damage before each use and an occasional cleaning, there are no maintenance requirements.
My preferred pneumatic shoring devices (comprising either a pin collar or outer ratcheting collar) with détente sphere attachments, also comprises a contiguous pressurized gas channel through the cylinder to the piston. In the best mode, this contiguous pressurized gas channel includes a circular channel segment along the lower floor surface of a cylinder rubber end cup.